That might be because mixing and matching different types of vaccines can often produce a stronger immune response, said Lawrence Young, a virologist at the University of Warwick in the United Kingdom.
After the AstraZeneca vaccine was linked to extremely rare blood clots, several European countries including Germany and France recommended people who got it as a first dose get a Pfizer or Moderna shot as a second dose instead. On Thursday, Canada made the same recommendation.
Britain says people should aim to get the same vaccine for their second dose if possible. If they got AstraZeneca as their first shot, they’re advised to get another vaccine only if they have a history of blood clots or other conditions that might put them at higher risk of clots.
According to Dr. Kate O’Brien, director of the World Health Organisation’s vaccine unit, the authorised COVID-19 vaccines are all designed to stimulate the immune system to produce virus-fighting antibodies.
She, however, noted that the way they do so varies.
“Based on the basic principles of how vaccines work, we do think that the mix-and-match regimens are going to work,” she said.
source: HealthWise